The present invention relates to an image forming apparatus, such as a laser printer, and a scanner apparatus incorporated in the image forming apparatus.
As electrophotographic type color laser printers, a tandem type color laser printer incorporating four photoconductor drums corresponding to yellow, magenta, cyan and black, respectively, has been known. In the tandem type color laser printer, toner images in the respective colors are formed substantially simultaneously on the respective photoconductor drums, and the toner images in the respective colors are transferred from these photoconductor drums to paper passing through the photoconductor drums one after the other so that the toner images are superimposed one upon the other. Therefore, a color image can be formed at substantially the same speed as in a monochrome laser printer.
In such a tandem type color laser printer, for example, a scanner employing a structure in which a plurality of light beams are deflected and scanned by a single polygon mirror may be incorporated as a scanner apparatus for forming an electrostatic latent image on each photoconductor drum.
Among scanner apparatuses of this type, there is a scanner apparatus that causes a plurality of light beams to be incident on different reflective surfaces of the polygon mirror from the same direction. There is also proposed a scanner apparatus that causes a plurality of light beams to be incident on different reflective surfaces of the polygon mirror (reflective surfaces on mutually opposite sides with respect to the rotation axis) from directions that are point symmetrical to each other with respect to the rotation axis of the polygon mirror (see, for example, Japanese Patent Application Laid-Open No. 2003-121775).